The instant invention relates to a process for forming a deposit on the surface of a metallic or conductive surface. The process employs a process to deposit, for example, a mineral containing coating or film upon a metallic, metal containing or an electrically conductive surface.
Silicates have been used in electrocleaning operations to clean steel, tin, among other surfaces. Electrocleaning is typically employed as a cleaning step prior to an electroplating operation. Usage of silicates as cleaners is described in xe2x80x9cSilicates As Cleaners In The Production of Tinplatexe2x80x9d is described by L. J. Brown in February 1966 edition of Plating; European Patent No. 00536832/EP B1 (Metallgesellschaft AG); U.S. Pat. Nos. 5,902,415, 5,352,296 and 4,492,616.
Processes for electrolytically forming a protective layer or film by using an anodic method are disclosed by U.S. Pat. No. 3,658,662 (Casson, Jr. et al.), and United Kingdom Patent No. 498,485.
U.S. Pat. No. 5,352,342 to Riffe, which issued on Oct. 4, 1994 and is entitled xe2x80x9cMethod And Apparatus For Preventing Corrosion Of Metal Structuresxe2x80x9d that describes using electromotive forces upon a zinc solvent containing paint; hereby incorporated by reference. U.S. Pat. Nos. 5,700,523, and 5,451,431; and German Patent No. 93115628 describes a processes for using alkaline metasilicates to treat metallic surfaces.
The disclosure of the previously identified patents and publications is hereby incorporated by reference.
The instant invention solves problems associated with conventional practices by providing an electroless process for treating metallic surfaces. By xe2x80x9celectrolessxe2x80x9d it is meant that no current is applied from an external source (a current may be generated in-situ due to an interaction between the metallic surface and the medium). The process employs a silicate medium having a controlled and predetermined silicate concentration, temperature and pH. As a result, the silicate medium that interacts with the metallic surface to form surface having one or more improved properties. The inventive process controls the medium""s characteristics and the surrounding environment in order to obtain a desired film or layer upon the metal surface, e.g, a film or layer having low surface porosity or high density. The characteristics of the film or layer can be controlled or modified by varying the temperature, pH, lattice builders (i.e., medium dopants), rate of formation, heat, pressure, pre and post treatments and silicate concentration.
The inventive process can form a surface comprising a mineral layer comprising an amorphous matrix surrounding or incorporating metal silicate crystals upon the substrate. The characteristics of the mineral layer are described in greater detail in the copending and commonly assigned patent applications listed below.
A metallic surface that is treated (e.g., forming the mineral layer) by the inventive process can possess improved corrosion resistance, increased electrical resistance, heat resistance, flexibility, resistance to stress crack corrosion, adhesion to topcoats, among other properties. The improved heat resistance broadens the range of processes that can be performed subsequent to forming the inventive layer, e.g., heat cured topcoatings, stamping/shaping, riveting, among other processes. The treated surface also imparts greater corrosion resistance (e.g., ASTM B-117), among other beneficial properties, than conventional tri-valent or hexa-valent chromate systems. The inventive process can provide a zinc-plate article having an ASTM B-117 resistance to white rust of at least about 96 hours (and normally greater than about 150 hours), and resistance to red rust of at least about 250 (and normally greater than about 400 hours). The corrosion resistance can be improved by adding a dopant to the silicate medium, using a rinse and/or applying at least one sealer/topcoating.
The inventive process is a marked improvement over conventional methods by obviating the need for solvents or solvent containing systems to form a corrosion resistant layer, e.g., a mineral layer. In contrast, to conventional methods the inventive process can be substantially solvent free. By xe2x80x9csubstantially solvent freexe2x80x9d it is meant that less than about 5 wt. %, and normally less than about 1 wt. % volatile organic compounds (V.O.C.s) are present in the electrolytic environment.
The inventive process is also a marked improvement over conventional methods by reducing, if not eliminating, chromate and/or phosphate containing compounds (and issues attendant with using these compounds such as waste disposal, worker exposure, among other undesirable environmental impacts). While the inventive process can be employed to enhance chromated or phosphated surfaces, the inventive process can replace these surfaces with a more environmentally desirable surface. The inventive process, therefore, can be xe2x80x9csubstantially chromate freexe2x80x9d and xe2x80x9csubstantially phosphate freexe2x80x9d and in turn produce articles that are also substantially chromate (hexavalent and trivalent) free and substantially phosphate free. The inventive process can also be substantially free of heavy metals such as chromium, lead, cadmium, barium, among others. By substantially chromate free, substantially phosphate free and substantially heavy metal free it is meant that less than 5 wt. % and normally about 0 wt. % chromates, phosphates and/or heavy metals are present in a process for producing an article or the resultant article.
The subject matter of the instant invention is related to commonly assigned Non-Provisional U.S. patent application Ser. No. 09/814,641, filed on Mar. 22, 2001 and entitled xe2x80x9cAn Energy Enhanced Process For Treating a Conductive Surface and Products Formed Therebyxe2x80x9d; Ser. No. 08/850,323, filed on May 2, 1997 and entitled xe2x80x9cCorrosion Resistant Coatings Containing An Amorphous Phasexe2x80x9d (Now U.S. Pat. No. 6,165,257); Ser. No. 08/850,586, filed on May 2, 1997 and entitled xe2x80x9cCorrosion Resistant Coatings Containing an Amorphous Phasexe2x80x9d (Now U.S. Pat. No. 6,143,420); Ser. No. 09/016,853, filed on Jan. 30, 1998 and entitled xe2x80x9cCorrosion Resistant Coatings Containing An Amorphous Phasexe2x80x9d (Now U.S. Pat. No. 6,190,779); Ser. No. 08/791,337, filed on May 31, 1997 and entitled xe2x80x9cCorrosion Resistant Coatings Containing An Amorphous Phasexe2x80x9d (now U.S. Pat. No. 5,938,976), Ser. No. 08/634,215, filed on Apr. 18, 1996, and entitled xe2x80x9cCorrosion Resistant Buffer System for Metal Productsxe2x80x9d, Ser. No. 08/476,271 filed on Jun. 7, 1995 and entitled xe2x80x9cCorrosion Resistant Buffer System For Metal Productsxe2x80x9d; and Ser. No. 08/327,438, filed on Oct. 21, 1994 and entitled xe2x80x9cCorrosion Resistant Buffer System For Metal Products, now U.S. Pat. No. 5,714,093.
The subject matter of this invention is related to Non-Provisional patent application Ser. No. 09/016,849, filed on Jan. 30, 1998 and entitled xe2x80x9cCorrosion Protective Coatingsxe2x80x9d. The subject matter of this invention is also related to Non-Provisional patent application Ser. No. 09/016,462, filed on Jan. 30, 1998 and entitled xe2x80x9cAqueous Gel Compositions and Use Thereofxe2x80x9d (now U.S. Pat. No. 6,033,495).
The subject matter of this invention is also related to Non-Provisional patent application Ser. No. 09/814,641, filed on Mar. 22, 2001, and entitled xe2x80x9cAn Energy Enhanced Process For Treating A Conductive Surface And Products Formed Therebyxe2x80x9d, and Non-Provisional patent application Ser. No. 10/211,029, filed on Aug. 3, 2002 and entitled xe2x80x9cAn Electrolytic And Electroless Process For Treating Metallic Surfaces And Products Formed Therebyxe2x80x9d, and Ser. No. 10/211,094, filed on Aug. 3, 2002 and entitled xe2x80x9cProcess For Treating A Conductive Surface And Products Formed Therebyxe2x80x9d.
The disclosure of the previously identified patents, patent applications and publications is hereby incorporated by reference.